1. Field of the Disclosure
This application generally relates to printing, and in particular, eliminating banding in semi-conductive magnetic brush developed images.
2. Description of Related Art
Banding in printing systems has been and will continue to be an engineering challenge in xerographic marking engines based on semi-conductive magnetic brush (SCMB) development as shown, for example, in U.S. Pat. Nos. 5,539,505 and 6,285,837 B1. Image banding is an image quality defect that consists of halftone density variation in the process direction and manifests itself as light and dark bands in the cross-process direction. Banding is largely due to fluctuations in the photoreceptor (PR) drum to magnetic roll spacing resulting from photoreceptor and magnetic roll run-out. Mechanical variations in the development nip from photoreceptor and/or magnetic roll run-out can modulate the developer nip density (mass on roll) and hence developability resulting in banding. Banding is not always apparent at time-zero, but may manifest itself as the developer ages. Hence, other material state factors, such as: toner concentration/triboelectricity; toner age; and possibly material processing and flow properties. Material state factors may magnify the effect of even small initially acceptable variations in photoreceptor drum to magnetic roll spacing although they are not well understood.
Consequently, banding has been a very difficult problem to overcome and a method is needed to compensate for this effect other than costly mechanical countermeasures involving tightening of parts tolerances.